I had the same problem- thought I'd fixed it by cleaning/tightening the gauge head, but really it's a waste of time.

Don't worry too much. IF you run out of oil pressure, your lifters will start clicking. You'll hear it.

I replaced it with a true gauge. I fear ripping the hose- which actually carries oil to the gauge- quite a bit, because it could leave you unable to drive, it'd spray out oil unless you pinch it with vise grips or whatever.

The gauge is nice, but it varies so much it IS difficult to conclude anything from it. It goes pretty low when warm and at a stop, and much higher on the road, and changes with RPM. Basically, if you don't hear the lifters getting noisy, it's enough, and I'm not sure what good this gauge does if I pay it no attention and would only rely on engine sound.